B7-33
Also known as: Single-chain relaxin-2 analog, RXFP1 agonist peptide
B7-33 (also called Single-chain relaxin-2 analog or RXFP1 agonist peptide) is a relaxin-2 analog in the RXFP1 agonist class. B7-33 is a single-chain minimised analog of human relaxin-2, engineered to retain receptor activity in a much smaller and more synthetically tractable molecule than the two-chain native hormone.
For research use only.
Key Facts
- CAS
- —
- Molecular Weight (MW)
- ~5 kDa
- Half-life
- Short; stabilized vs native relaxin-2
- FDA status
- Investigational New Drug (IND)
- Administration Route
- —
- Frequency
- —
- Last updated
- Aug 30, 2026
- Reviewed
- Aug 30, 2026
- Targets
- RXFP1 (relaxin family peptide receptor 1)
Research summary
Single-chain relaxin-2 analog designed at Monash University as an RXFP1 agonist for anti-fibrotic and vasodilatory research. Preclinical; not FDA-approved.
Peptide Library's B7-33 profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Protocol
- Dosage Range
- Per research protocol
- Frequency
- —
- Cycle
- —
- Administration Route
- —
- Reconstitution Guide
- —
- Timing Notes
- Studied for anti-fibrotic / vasodilatory effects.
Not yet checked against primary sources
These figures are compiled from earlier reference material. They have not been verified against FDA labelling, registered trials or published literature, no citation is attached to them, and none of them is a recommended dose. B7-33 is queued for dosage evidence review.
Compare reported doses across the whole librarySequence & molecular data
| Molecular formula | Synthetic single-chain peptide (≈5 kDa) |
|---|---|
| Molecular weight | ~5 kDa |
| Half-life | Short; stabilized vs native relaxin-2 |
| Appearance | White lyophilized powder (research) |
| Formulation | Lyophilized Powder |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
B7-33 is a single-chain minimised analog of human relaxin-2, engineered to retain receptor activity in a much smaller and more synthetically tractable molecule than the two-chain native hormone. It activates RXFP1, a G protein-coupled receptor expressed on vascular smooth muscle, endothelium and fibroblasts. A notable feature reported for B7-33 is biased signalling: it favours the ERK1/2 pathway over the cyclic AMP pathway that native relaxin also engages, which has been proposed to underlie antifibrotic activity with less of the vasodilatory response. In cardiac and renal models this manifests as reduced collagen deposition and matrix remodelling. It is preclinical with no human data.
Origin
Engineered single-chain human relaxin-2 analog.
Targets
Studies
- The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy
- B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice
- Coatings Releasing the Relaxin Peptide Analogue B7-33 Reduce Fibrotic Encapsulation
- B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin)
- Single chain peptide agonists of relaxin receptors
Regulatory & research status
B7-33 has been studied under an Investigational New Drug application. It is not approved for marketing.
| FDA status | Investigational New Drug (IND) |
|---|---|
| Availability | Research-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | Clinical Trial |
Benefits
B7-33 side effects
Side Effects
- No established human dose
- Hypotension theoretical
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
B7-33: frequently asked questions
What is B7-33?
Single-chain relaxin-2 analog designed at Monash University as an RXFP1 agonist for anti-fibrotic and vasodilatory research. Preclinical; not FDA-approved.
How does B7-33 work?
B7-33 is a single-chain minimised analog of human relaxin-2, engineered to retain receptor activity in a much smaller and more synthetically tractable molecule than the two-chain native hormone. It activates RXFP1, a G protein-coupled receptor expressed on vascular smooth muscle, endothelium and fibroblasts.
Is B7-33 FDA approved?
No. B7-33 is investigational: it is in clinical development and has not been approved by the FDA for any indication. Investigational status means trials are ongoing or complete but regulatory review has not resulted in approval, and efficacy and safety are still being established.
What is the half-life of B7-33?
Reported half-life for B7-33 is Short; stabilized vs native relaxin-2. Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.
References
- The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy — Biomed Pharmacother, 2023External reference
- B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice — J Am Heart Assoc, 2020External reference
- Coatings Releasing the Relaxin Peptide Analogue B7-33 Reduce Fibrotic Encapsulation — ACS Appl Mater Interfaces, 2019External reference
- B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin) — Eur J Pharmacol, 2017External reference
- Single chain peptide agonists of relaxin receptors — Mol Cell Endocrinol, 2019External reference
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Aug 30, 2026 · Version 1
This B7-33 profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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